The present invention relates to guiding of storage tape in a tape transport system. More particularly, it relates to a subambient pressure feature for attenuating high frequency lateral tape motion at high tape speeds within a tape transport system, for example, a data storage tape cartridge and/or a tape drive. 
Data storage tape cartridges have been used for decades in the computer, audio, and video fields. The data storage tape cartridge continues to be an extremely popular form of recording large volumes of information for subsequent retrieval and use. 
One type of data storage tape cartridge consists generally of an outer shell or housing maintaining two tape reels, two or more corner guides, and a length of magnetic storage tape. The storage tape is wrapped about and extends between the two tape reels along a tape path defined, in part, by the corner guides. In this regard, the corner guides extend the tape across a head access window (or read/write zone) formed in the housing. In particular, the corner guides are positioned at opposite sides of the head access window to direct the tape path therethrough. These two corner guides are typically “compliant guides,” each providing an arcuate guide surface and opposing tape edge (or lateral) stop surfaces, one of which is compliant. Other guides may be provided within the housing to direct the storage tape between the tape reels and the corner guides associated with the head access window. Regardless, a door is normally associated with the head access window to provide selective access to  the storage tape. During use, the cartridge is inserted into a tape drive, and the door is maneuvered into an open position. A transducer, such as a magnetic read/write head, interfaces with the storage tape via the head access window. To ensure consistent, accurate engagement by the read/write head, the storage tape must be precisely positioned within the head access window. Similar concerns can arise with a single reel cartridge configuration where the storage tape is driven between the cartridge reel and a take-up reel within the tape drive. 
Various inherent design issues may compromise desired, precise positioning of the storage across the read/write head. For example, the tape reel(s) may contribute to unexpected lateral (or edge-to-edge) tape movement. In this regard, the typical tape reel includes a central hub and opposing flanges. The storage tape is wrapped about the central hub and is laterally constrained by the flanges (i.e., the flanges limit lateral movement of the storage tape by contacting a respective top or bottom edge). However, so as to not overly contact the tape edges, a slight tape edge-to-flange spacing is normally presented. That is to say, an overall lateral spacing between the opposing flanges is greater than a height of the storage tape, typically by 0.002–0.02 inch. As a result, during tape reel rotation, the storage tape may move laterally from flange-to-flange. This is especially true during data transfer operations in which the outer-most layers of the storage tape are normally not tightly wrapped about the tape reel hub. In other words, a “slack” is developed in the storage tape, such that the storage tape easily moves laterally between the opposing flanges. This unforeseen lateral movement is “seen” by the head, leading to read/write errors. 
The corner guides cannot readily correct this unexpected lateral movement in that the guide surfaces associated with the corner guides are configured so as to not frictionally engage the storage tape at relatively high tape speeds, such as those encountered in the data transfer mode of operation. This is especially true with large diameter corner guides. At tape speeds in excess of 1 meter/second, an air bearing is generated between the guide surface and the storage tape such that the storage tape “flies” over the guide surface or otherwise  experiences hydrodynamic lift. Thus, the guide surface does not and cannot frictionally dampen lateral tape movement. As previously described, compliant tape guides typically incorporate opposing, transverse flange surfaces that present “hard stops” to lateral tape movement. These transverse surfaces effectively angularly redirect lateral movements in the storage tape. In other words, a storage tape that has moved laterally along a tape reel will deflect at the associated compliant guide transverse surface, rendering the storage tape skewed or off-center with respect to the head. An additional concern is edge wear on the tape due to contact with guide flanges, including potential buckling of the tape edge. 
Any slight deviation (or skew) from a desired planar positioning of a storage tape within the head access window may result in reading/writing errors. If the storage tape is slightly above or below an expected location, the read/write head will experience difficulties in finding a desired track on the storage tape. Additionally, with closed loop servo control systems, the read/write head may encounter tracking problems, whereby the head “loses” a desired track (commonly referred to as “servo off track event”). Importantly, with recent improvements in storage tape media that have increased available track densities, the likelihood of lateral movement-caused errors has similarly increased. 
Magnetic tape systems continue to be highly popular. While the evolution of cartridge components, including the storage tape and compliant guides, has greatly improved storage capacity and cartridge performance, other problems, including lateral tape movement, remain. Therefore, a need exists for a tape transport system configuration adapted to dampen lateral storage tape movement during use, particularly at high tape speeds, such as within a data storage tape cartridge and/or a tape drive. 